Ocular: Nasolacrimal System Flashcards
What is the purpose of the nasolacrimal system?
to drain tears from the ocular surface to the lacrimal sac
Where does the nasolacrimal system ultimately end?
Nasal cavity
What are the tears produced by?
Palpebral portion of the lacrimal gland
Where is the start of the nasolacrimal system?
Lacrimal gland in the superior lateral portion of the orbit
where is the end of the nasolacrimal system?
Inferior nasal meatus of the nasal cavity
Blockage of the nasolacrimal system can cause what?
Tears to overflow, called epiphora
What type of gland is the lacrimal gland?
Exocrine gland
Where is the aqueous portion of tears released into?
the fornix
Palpebral portion of the lacrimal gland contains ____ ducts. They come from _______ and _________ portions open into the _______
12 ducts, orbital and palpebral portions , fornix
What portion of the lacrimal gland is biopsies in lacrimal gland tumor? why?
Orbital portion in order to avoid ducts
What cells make up the lacrimal gland?
Many tiny acini cells
Acinar cells =
Merocrine secretory cells
What surrounds the acini?
Discontinuous ring of myoepithelial cells
What does the matrix around the acini cells contain?
-T cells
-B cells
-plasma cells
What vessels supply the lacrimal gland?
-lacrimal artery
-lacrimal vein
-lymphatics drains into into pre-auricular
Parasympathetic nerve supply to the lacrimal gland causes…
Production and release of aqueous tear compartment
Sympathetic nerve supply to the lacrimal glands controls…
Vascular tone within the gland
What provides sensory innervation to the lacrimal gland?
Lacrimal nerve of v1
Where does reflex or emotional tearing come from?
Main lacrimal gland
Where does basal tear production occur?
Accessory lacrimal glands (Wolfring and krause)
Order of the nasal drainage system:
-punctuated
-canaliculi
-lacrimal sac
-nasolacrimal duct
-valve of hasner
Can people’s canaliculi come together?
Yes
Canaliculi takes ___mm down (or up) and ___ mm across
2mm, 8mm
What are the puncta?
Tiny apertures where tears drain into the canaliculi
Where are the puncta located?
Medially in a mild elevation of the upper and lower lids and do face the globe slightly
Which puncta is larger?
The lower lid
What is the function of punctual plugs?
Halt or slow the tear drainage to reduce ocular surface dryness
What is punctual stenosis and when does it occur?
Narrowing of the punctual opening that can occur with aging
Function of the canaliculi
Connect the puncta to the lacrimal sac
What tissue is located in the walls of the canliculi?
Elastic tissues so they can dilate
What muscle encircles the canaliculi?
Horner’s muscle
Parts of the canaliculi:
-vertical
-horizontal
-common canaliculi (enters lacrimal sac)
What is the valve of rosenmuller?
A stricture created by an angle where the common canaliculus enters the lacrimal sac
What happens if the angle in the valve of rosenmuller not sufficient?
Reflux of air comes out of the puncta during sneezing
Where is lacrimal sac located?
In the lacrimal fossa
Lacrimal fossa bordered anteriorly by____________ and posterioly by _______________
Anterior lacrimal crest of maxilla, posterior lacrimal crest of lacrimal bone
Preseptal cellulitis
Infection in front of septum
Orbital cellulitis
Infection behind the septum
Nasolacrimal sac enters into the___________
Nasolacrimal duct
How long is nasolacrimal duct? Where does it empty?
-15mm long
-empties into inferior meatus
What is the valve of hasner?
Hinge tissue that normally hangs downward allowing for tear flow into nasal cavity
If pressure in nasal cavity is greater than the nasolacrimal duct then the valve of hasner is pushed _______________ stopping nasal contents from entering nasolacrimal duct
Laterally
Congenital NLDO is caused by what?
Failure of NLD to canalize by birth (valve of hasner incomplete)
In congenital NLDO, stagnant tear fluid can lead to…
Infection
What is Dacryocytocele?
Very rare simultaneous obstruction at hasner and rosenmuller valves
Dacryocytocele leads to…
Accumulation of mucoid fluid in lacrimal sac
What can dacryocystorhinostomy used for?
-In an acquired nasolacrimal duct obstruction
-a connection between the lacrimal sac and nasal cavity can be made to bypass NLD
Tear drainage theories agree on which concept?
That the drainage of tears relies on the contraction of the muscle causing canaliculi compression/shortening
Tear drainage theories disagree on what concept?
Whether the contraction of orbicularis causes lacrimal sac compression or expansion
Orbicularis contraction expands lacrimal sac theory->insists that contraction of the ___________muscle pulls the lacrimal sac open?
Horner muscle
Lacrimal sac wedge tear drainage theory insists that the contraction of ______________ muscle compresses the lacrimal sac
Orbicularis muscle
In the HYPOTHESIS of tear drainage, What happens before a blink?
Capillary action moves the tears into the puncta
During the lid closing of the tear drainage HYPOTHESIS,what happens?
-Puncta meet and close
-Horners muscle compresses canaliculi and sac casusing tears to move to area of lower pressure
During the lid reopening in the tear drainage HYPOTHESIS, what happens?
Canliculi and sac expand again and creates a negative pressure
During the end of a blink in the tear drainage HYPOTHESIS, what happens?
The negative pressure sucks the tears through the puncta towards the sac
